1. Field of the Invention
Example embodiments of the present invention relate to spatial light modulators (SLMs) and methods for addressing the same.
2. Description of the Related Art
Related art micro-electromechanical systems (MEMS) may include movable mirrors fabricated on wafer substrates using micro-electronic processing techniques. In these related art MEMS, electrostatic actuation may be used to deflect the micro-mirrors. For example, a voltage may be generated between two electrodes, one of which is stationary and the other of which positioned on the mirror, in order to produce a force between the two electrodes.
A related art SLM with an array of actuators (e.g., micro-mirrors, reflecting elements, modulating elements, pixel elements, etc.) used in, for example, a mask writing tool or a chip manufacturing tool may be loaded with a specific pattern. Each actuator may be in an addressed state or a non-addressed state before respective stamps may be printed. This pattern may be a subset of the pattern to be printed on the mask or chip, respectively. Each actuator mirror may be deflected electrostatically by applying voltage between the mirror and an underlying address electrode, after which the actuator mirror may move into a deflected state before an electromagnetic radiation source may be triggered to print the stamp.
An SLM may be loaded in an analogue mode by applying one potential to the mirrors and individually addressing at least one electrode belonging to each of the mirrors in order to create a pattern of the SLM. In the analogue mode, the SLM mirror may be set to a number of different states, for example, 64 or 128 states ranging from non-deflected (e.g., completely non-deflected or minimum deflection) to a higher (e.g., maximum) deflection. A maximum deflection may be a state in which little or no electromagnetic radiation impinges on the micro-mirror, and minimum deflection may be defined as full reflection of the impinged electromagnetic radiation.
In a related art digital SLM, maximum deflection may be when the reflected electromagnetic beam is deflected out of the target plane and minimum deflection may be full reflection of the impinged electromagnetic radiation. Related art digital SLMs operate in a deflection mode, while related art analogue SLMs operate in a diffraction mode. The degree of deflecting individual elements may vary between those digital and analogue SLMs, where the analogue SLMs may be deflected parts of a degree and the digital SLMs may be deflected several degrees.
FIG. 3 illustrates a side view of a related art actuator 300. As shown in FIG. 3, the actuator structure 300 may be, for example, a micro-mirror structure in a spatial light modulator (SLM), and may include a substrate 313, a first electrode 312, a second electrode 314, a support structure 311 and a movable element 310. The substrate 313 may be made of semi-conducting material and may comprise one or a plurality of circuits (e.g., CMOS circuits). The first and second electrodes 312 and 314 may be made of an electrically conductive material, for example, gold, copper, silver, alloys thereof and/or other electrically conductive materials. The electrodes 312 and 314 may be connectable to steering circuits, such as, the above-mentioned circuit.
The support structure 311 may be manufactured of a stiff (e.g., relatively stiff) material, for example, single crystal silicon or any similar, or substantially similar materials. The movable element 310 may be manufactured of a material having suitable (e.g., good) optical properties, for example, aluminum or any other suitable metallic material. Alternatively, a material without the above characteristics may be coated with one or a plurality of other materials having suitable characteristics, and a sandwich structure may be created.
An electrostatic force may deflect the movable element 310. Applying different potentials on the movable element 310 and the first electrode 312 or second electrode 314 may create electrostatic force. When a first potential is applied to the movable element 310 and a second (e.g., different) potential is applied to the first and second electrodes 312 and 314, an electrostatic force may be generated, but may not deflect the movable element 310, for example, because the attractive force, which may be attractive independent of the polarity of the potential difference, between the first electrode 312 and the mirror may be equivalent, or substantially equivalent, to the attractive force between the second electrode 314 and the same mirror. The two attractive forces may equalize each other.
In FIG. 3 the actuator structure may include the first 312 and second 314 electrodes. However, deflecting the movable element 310 may require one electrode, either the first electrode 312 or second electrode 313. However, two electrodes arranged spaced apart from each other may allow the mirror to be deflected in two different directions.